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| Mid-September can be toasty in SoCal |
During our first summer of owning a 2013 Focus Electric, the benefits of having a variable-load A/C compressor in terms of energy use have become noticeable as I've observed the Focus Electric's user-configurable Climate energy use display. On days like today, when air temperatures on the asphalt here in Los Angeles exceed 110°F, the Climate gauge peaks at over 4 kilowatts of power when I first turn on the cooling in the hot car. But after running for only 5 to 10 minutes, I can maintain a comfortable cabin (at least in the front seats, with the A/C ducts blowing cool air directly on us) by eventually dropping the fan to its lowest speed - where the display indicates that the Climate system is consuming well under 1.0 kW. In the past, A/C compressors were not variable-load. They were on or off, and temperatures were either modulated by duty-cycling the compressor with an electrically-activated clutch, or by mixing engine coolant-heated air.
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| Just after entering the Focus Electric in 110°F temps, the Climate system works hard to cool the cabin, using nearly 5 kW. But within minutes, the HVAC system can maintain comfortable temps at under 1 kW. |
I wrote previously that I do NOT use the automatic thermostat in our Focus Electric in hot weather, leaving the temperature set to "LO" to avoid the HVAC system activating its high-wattage heater to regulate the amount of cooling. I've practiced that for this entire summer, and the strategy works, except that sometimes it gets too cold when temps are merely "very warm" (85-90F), and even pointing the vents away from passengers and turning the fan all the way down doesn't moderate the cooling enough. This demonstrates how effective and impressive the DENSO-based A/C is, but how Ford still should have some way to regulate cooling without turning on its 6+ kW heater. When it's 82F outside and muggy, running the A/C at "LO" will make it really cold inside, and turning the A/C switch OFF results in immediately sticky conditions in the cabin.
And as we head into winter, I'm reminded that the Defrost system appears to run both A/C compressor and heater to clear the windows. This is a typical strategy of all cars, but because the Focus Electric's cabin heater is electrically-powered, and uses a devastating amount of power (while heat in traditional cars is scavenged from the engine cooling system), a driver has no choice but to run the range-sapping defroster in order to maintain fog-free window interiors for safety.
So bravo to DENSO for what appears to be a superb solution for efficiently compressing refrigerant with electricity. I've been able to maintain the same 245 Watt-hours/mile consumption rate that I'd averaged in the winter and spring months before hot weather arrived. I've read that electric A/C compressors are a trend among all motor vehicles, and I'm encouraged by our own experiences.
